MOL. WT. Molecular weight.
M.P. Member of Parliament.
M.P.S. Member of the Philological Society.
M.P.S. Member of the Pharmaceutical Society.
M.R. Master of the Rolls.
MR. Master or Mister.
M.R.A.S. Member of the Royal Asiatic Society.
M.R.A.S. Member of the Royal Academy of Sciences.
M.R.C.C. Member of the Royal College of Chemistry.
M.R.C.P. Member of the Royal College of Preceptors.
M.R.C.S. Member of the Royal College of Surgeons.
M.R.C.V.S. Member of the Royal College of Veterinary Surgeons.
M.R.G.S. Member of the Royal Geographical Society.
M.R.I. Member of the Royal Institution.
M.R.I.A. Member of the Royal Irish Academy.
MS. Manuscript;--MSS., Manuscripts.
M.S. Master in Surgery; _Memoriae Sacrum_=Sacred to the Memory.
M.S. Months (after) sight.
M.S.C. Madras Staff Corps.
M.S.L. Mean sea-level.
M.S.S. Member of the Statistical Society.
MT. Mount;--MTS., Mountains.
MUS. Music; Museum.
MUS.B. Bachelor of Music.
MUS.D., DOC., DOCT. Doctor of Music.
M.V.O. Member of the Royal Victorian Order.
N. North, Northern; Nitrogen.
N. Name; _Natus_=Born; Neuter; Noon.
N.A. North America.
NAT. HIST. Natural History.
NAT. ORD. Natural order.
NAV. Naval; Navigation.
N.B. North Britain, North British; New Brunswick.
N.B., _nota bene_=Note well, or take notice.
N.C. North Carolina; New Church.